The present invention relates to orthopedic implants and to methods of treating bone defects. More specifically, but not exclusively, the present invention is directed to non-metallic orthopedic implants, methods for intra-operative assembly of the orthopedic implants, and methods of internal fixation of bone tissue to facilitate medical treatment.
It is known to use orthopedic implants, such as plates, rods, and screws, to repair and treat bone defects, such as cracked and broken bones, and disorders of the musculo-skeletal system. In the past, many of the orthopedic implants were formed primarily of metallic materials. The metallic implants offer many advantages. They can be readily sterilized, are biocompatible, and provide the requisite strength for support and/or fixation of the bony tissue. However, metallic implants also exhibit a significantly greater compressive modulus over cortical bone. The metallic implant can stress-shield new bone growth to induce osteoporosis and/or osteopenia, resulting in cortical bone that is prone to refracture. After the bone defect was repaired, often the implants were no longer needed to maintain the patient""s mobility. While some metal implants were allowed to remain in place, many were removed. Their removal required a second surgical procedure. Obviously, it would be more desirable to eliminate the second surgical procedure to minimize patient pain/discomfort, chance of infection, and subsequent trauma to the newly healed site, while at the same time removing the implant as a potential source of irritation for surrounding tissue.
More recently, new treatment methods and improved materials, including non-metallic implants, have been used to treat bone defects. The non-metallic implants can remain in the body, or alternatively, selected implants can be made of materials that biodegrade over a time period ranging from a few days to several months.
While the new materials have provided significant advances over the previous medical devices, there still remain significant problems requiring continued development for non-metallic medical implantsxe2x80x94not the least of which is their lower of mechanical strength compared with their metallic counterparts. Typically, non-metallic orthopedic implants have not provided sufficient strength to be used alone for internal fixation of load-supporting bone tissue, such as the long bones of the upper and lower limbs and the spine. Further, selected non-metallic implants such as bone plates can fail when installed with non-metallic bone fasteners. Reduced friction between contacting surfaces of fastener and bone plate; lower mechanical strength; lower holding force; and in selected materials, biodegradation of the implants themselves, to name a few examples, all can contribute to an unacceptable failure rate for the non-metallic implants. Even metallic fasteners have been known to dislodge or back out from the implant and/or bone tissue. The non-metallic fasteners can be even more prone to dislodge. The non-metallic fasteners cannot be tightened or torqued sufficiently to prevent the fastener from disengaging from the plate. The non-metallic bone screws do not exhibit the mechanical strength of metal counterparts, and typical mechanical lock mechanisms and techniques often fail to maintain an integral connection with non-metallic fastenersxe2x80x94requiring revision surgery. This can be acerbated for implants formed from biodegradable materials, which successively degrade over time and which become increasingly weaker as they degrade. These are but a few of the problems faced by patients and their physicians in selecting an appropriate course of treatment.
In light of the above-described problems, there is a continuing need for advancements in the relevant field, including improved methods, compositions and devices to provide non-metallic implants that exhibit a high rate of successful orthopedic and musculoskeletal treatment and yet reduce necessity for subsequent surgical intervention. The present invention is such an advancement and provides a wide variety of benefits and advantages.
The present invention relates to orthopedic implants and to the manufacture and use thereof. Various aspects of the invention are novel, nonobvious and provide various advantages. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain forms and features which are characteristic of the preferred embodiments disclosed herein are described briefly as follows.
In one form, the present invention provides an implant assembly that comprises a bone plate having at least one opening extending therethrough and a bone fastener received within the opening. The bone fastener has a proximal head, a bone engaging distal portion and a shaft therebetween. The fastener, the bone plate, or both, are formed of a polymeric material capable of deforming to fixedly interengage the fastener to the bone plate.
In another form, this invention provides an implant assembly that comprises a bone plate having an opening extending therethrough, and a fastener that is received within the opening. The fastener has a head, a threaded distal portion and a shaft therebetween. At least a portion of the fastener is formed of a polymeric material capable of swelling upon contact with body fluid to fixedly secure the fastener to the bone plate.
In another form, this invention provides an implant assembly comprising a bone plate having at least one opening extending therethrough, and a fastener that is to be received within the opening. The fastener has a proximal head, a distal bone engaging portion and a shaft therebetween. At least one of the fasteners and the bone plate include an adhesive to fixedly interengage the fastener to the bone plate.
In yet another form, this invention provides a method of fixedly securing a fastener to a bone plate. The method comprises surgically preparing bone tissue in need of repair for receipt of a bone plate; placing a bone plate having at least one opening proximal to the bone tissue in need of repair; and inserting a fastener through the opening and into the bone tissue. At least one of the fastener and the bone plate is deformed to fixedly secure the bone screw to the bone plate.
In still yet another form, this invention provides a method of fixedly securing a bone screw to a bone plate. This method comprises surgically preparing bone tissue in need of repair for receipt of a bone plate; placing a bone plate having at least one opening therethrough proximal to the bone tissue; and inserting a bone screw through the opening and into the bone tissue. At least one of the fastener and the bone plate include an adhesive to fixedly secure the fastener to the bone plate.
Further objects, features, aspects, forms, advantages and benefits shall become apparent from the description and drawings contained herein.